Wound core stationary induction apparatus



June 17, 1941. F. BRAND 2,246,240

WOUND CORE STATIONARY INDUCTION APPARATUS Original Filed March 22, 19382 Sheets-Sheet l EDD Ff .12. 25 4s 24 27 Inventor: Frederick E Brand Histtorneg.

June 17, 1941. F. F. BRAND WOUND CORE STATIONARY INDUCTION APPARATUS 2Sheets-Sheet 2 Original Filed March 22, 1938 Patented June 17, 1941UNITED STATES PATENTOFFICE WOUND CORE STATIONARY INDUCTIOlW APPARATUSFrederick F. Brand, Pittsfleld, Mass., assignor to -Gen eral ElectricCompany, a corporation of New York Original application March 22, 1938,Serial No.

Divided and this application December 19, 1940, Serial No. 370,894

1 Claim. (01. 175-356) relatively low magnetizing currents.

It is an object of my invention to provide such apparatus in which thecost of materials and the cost of manufacturing operations arerelatively low.

Other and further objects and advantages will I become apparent as thedescription proceeds.

In carrying out my invention in its preferred form I utilize a currentconducting winding or a winding structure including a plurality ofwindings which has already been wound from current conductors andinsulated, and I form a magnetic core for such a winding structure bywinding into it one or more strips of magnetic sheet material. Themagnetic strip material is wound spirally fiat-wise to form an annularcore.

In order to remove strains from the magnetic material and give it a setwhich retains it in its completed form, a core is first wound from thestrip material on to a mandrel which has such a diameter that the coreso formed would fit closely around the insulated leg of the winding towhich it is later to be applied if it could be transferred directly fromthemandrel to the winding structure. Such'a core is then heat treated orannealed and after the heat treatment has been be stressed beyond itselastic limit or so as to inis a modification of that previouslyinvented by John C. Granfield and described in his copending applicationSerial No. 123,249, filed January 30, 1937-Electromagnetic inductionapparatus and method of making the same-assigned to the same assignee asthe present application and resulting in Letters Patent 2,160,588,granted May 30, 1939.

The invention will be understood more readily from the followingdetailed description when considered in connection with the accompanyingdrawings, and those features of the invention which are believed to benovel and patentable will be pointed out in theclaim appended hereto. Inthe drawngs,- Fig. 1 is a perspective view of a coil of magnetic stripmaterial wound to form a troduce an appreciable permanent deformation Iin the material. An insulating cylinder or wincling form is then placedaround the current conducting winding and the strip is wound on to thisform from the temporary coil by rotating the Winding form and the layersof strip material as they come on to the form. The relative position bfthe layers of strip material is reversed in the temporary coil and, asthe strip material comes around the current conducting winding theoriginal order of layers is reassumed so that when the core is in placeon the current conducting Winding it has the same shape and the samerelationship of layers as when heat treated. Consequently, the magneticstrip material is free from strains and has the shape which it tends toas sume by reasonof the set produced during the heat treatment. My corewinding arrangement core for use in stationary induction apparatus inaccordance with my invention. Figs. 2, 3, and 4 are diagramsillustrating shapes to which the ends of the strip material may be cutfor convenience in handling and fastening. Fig. 5 is a diagramillustrating one step in the process of preparing the strip material forwinding on to the current conducting winding structure. Fig. 6 is a planview of the strip material wound into a temporary coil. Fig. 7 is a planview of a clip which may be used for fastening the end turn of thetemporary coil. Fig. 8 is a side view of the temporary coil of Fig. 6with the clip of Fig. 7 in place. Fig. 9 is a diagram illustrating afurther step in the operation of winding the strip material on to thecurrent conducting structure and showing one form of machine which maybe winding structure broken away on either side of the wound strip core.Fig. 15 is a perspective view of one embodiment of my invention showinga winding structure with one magnetic core in place. Fig. 16 is anelevation of a transformer constructed in accordance with my inventionhaving two wound strip cores. Fig. 17 is an elevation of a transformerhaving a single wound strip core. Like reference characters are utilizedthroughout the drawings to designate like parts. V

The current conducting winding structure or the manner in which it isproduced does not conrial for winding on to the current conductingwinding II, I form the strip material into a coil I2 such as shown inFig. 1, separate. from the current conducting winding structure, but ofthe same shape and size as it is to have in the completelyvassembledapparatus. Although I have shown the coil I2 as a circular annulus, itwill thereto and does not exclude the use of rectangular, elliptical, oroval annuli or rings, e. g., provided the original coil of strip has thesame shape and size as it is to have. in the finished electromagneticinduction apparatus. Preferstrip material on to a mandrel I3 such asrepresented in Fig.. 5. Preferably means are provided for holding thecoil I2 in tightly wound condition, such as a strap or clip or, ifdesired, tack welds such as those at 46 in Fig. 14 may be used. Thewound core is then subjected to a suitable annealing process or heattreatment at such aomitted in the case of winding structures alreadyhaving a tough insulation, I prefer to utilize such a cylinder forfacilitating the operation of the winding. Various forms'of insulatingor merely protecting cylindersmay be utilized. For example. as shown inFigs. 9 and 12,"

' I may utilize a cylinder 22 cut open at 23, and

be understood that my invention is not limited ably, the coil of Fig. 1is produced by winding composed of material which is sufiicientlyflexible topermit the cylinder 22 to be opened and placed around thewinding leg 20. In case a protecting cylinder of still or rigid materialis to be employed, the cylinder may take the form shown in Fig. 10consisting of two halves 24 with two breaks at 25 and 26,or adoublelayer cylinder. may be utilized as shown in Fig. 11 in which thepieces 24 are augmented by another pair of cylinder halves 21 placedwithin the first pair and having breaks 28 and 29 displaced 90 degreesfrom the breaks 25 and 28 in the outer pieces 24.

When an insulating cylinder such as the cylinder 22 has been placedaround the winding leg 20, the coil I4 is opened and the end 30 of thestrip is secured thereto, or one turn of the magnetic strip is passedaround the cylinder 22 so that rotation of the cylinder and the firstlayer of the magnetic strip causes strip material to be wound oil thetemporary coil I4 and temperature and for such a length of time as toremove all strains and to give the material a definite set for retainingthe shape which it has in the coil shown inFig. 1. After the heattreatment has" been completed andthe coil of ma netic strip has cooledany fastening means are removed or tack welds, if used, are broken andthe strip is unwound and formed into a temporary coil I4, in which thecurvature of the strip is in the same direction as in the coil, I2, as

on to the insulating cylinder 22 with the turns of the final coil ofstrip in the same sequence as in the original coil of strip which wasannealed. This operation may be performed by hand by rotating the end 33and the insulating cylinder 22 with it until the completed core I2 hasbeen produced as shown in Figs. 13 and 14. For the sake of carrying outthe operation at greater speed and with less labor in the case of largeapparatus, a winding machine such as shown in Fig. 9 mai be employedhaving suitable sup-- ports, not shown, for the temporary coil I4 andshown in Figs. 5 and 6. This may be done, ii .desired, by gripping theend portion I5 of the magnetic strip between two rollers I6 and I1 andpassing it back under to form a loop I8. One-of the rollers l6 and I1 ispower driven, or if desired, both may be power driven.

The diameter of the inner loop I8 of the temporary coil I4 is so chosenthat the material in' the strip will not be stressed appreciably beyondits elastic limit. Ordinarily, this is accomplished most conveniently bymaking the inner the innerdiameter of the coil I2, In the ardiameter ofthe temporary coil I4; greater than rangement shown, the inner diameterof the coil I4 is approin'mately equal to the outer diameter of the coilI2. However, it will understood that in the case of certain materials.satisfactory results may be obtained by making the inner diameter of thecoil I4 less than the inner diameter ofthe coil l2 If desired, thediameter of the roller l6-may be made equal to the inner diameter of thecoil I4, so that the roller I6 becomes a mandrelon to which thetemporary cofl I6 is .wound. material in the shape shown in Fig 6,preparatory to the-next operation, the outer end 'of the strip may betack welded to the outer surface of the next layer of strip material, orif desired, a clip I9 such as shown in Fig.7 may be. snapped over thecoil I4. I

w The next operation consists of placing a suitable insulating cylinderor tube around the leg 20 of a winding structure II around which themagnetic core is to be wound. Although the use In order to hold thestrip thewinding leg 20 and adjustable power driven rollers 3| adaptedto engage the strip frictionally. The rollers 3| may be carried by arms(not shown) pivoted at 32 and 33 so that as the wound coil being formedincreases in size, the rollers 3| may move apart. For driving therollers 3| there are provided a motor driven gear box 34 having shafts35 and 36 rotating in opposite directions, pulleys 31 and 33 eachconnected to one of the rollers 3|, pulleys 39 and 40, belts 4| and 42joining pulleys 31 and 33 to pulleys 39 and 40. respectively, and bevelgearings 43 and 44 coupling the oppositely rotating shafts 35 and 33 tothe pulleys and 43, respectively, in order to drive the rollers 3| inthe same angular direction.

Any suitable means may be provided for securing the end 30 of the stripto the insulating cylinder 22 when starting a winding operation,

' for example, the end of the strip may be bent down at an angle of 90degrees or a hook may width of the end of the strip as shown in Figs. 3and 4 may be helpful. However, I have found that satisfactory operationmay be obtained by merely crimping the strip near the end 30 to form thecrimp 45 as shown in Figs. 9 and 12.

The crimp 45 drops into the break 23 or 25 in the insulating cylinder'22 or 24 and facilitates 'the winding operation at the start. I havefolmd that if one or more convolutions of the steel strip be woundtightly on the insulating cylinder 22 or 24, and pressure be applied tothe outer con.- volution by rollers 3|, that the friction of the innerconvolution on the cylinder is sufiicient to permit rapid winding of thecomplete coil of strip upon the cylinder. The deformation of the end ofthe strip to engage a recess in the cylinder is a means to facilitatethe winding opera-' terial which may be used to produce stationaryinduction apparatus having low losses magnetizing current, I now believethatthebe st. results may be obtained by utilizing high reduction,cold-rolled silicon steel. Good results may also be obtainedwith anickel-iron alloy. The high reduction, cold-rolled silicon strip withwhich I have obtainedthe best results has a silicon content of about 3percent. The process of cold-rolling a magnetic strip with a highreduction is disclosed, for example, in Patent 1,915,766 of January 27,1933, to Smith et al., patents to Freeland 1,932,306-7-8-9 of October24, 1933, and Goss Patent 1,965,559 of July 31, i

1934. The process is a general one applicable to nickel-iron alloys andsilicon steel and is, in brief, characterized by hot-rolling to athickness considerably greater than the finished size followed byannealing, and a further reduction of about so per cent by cold-rollingto the finished size and then heat-treating. The quality, if desired,may be improved somewhat by a further step of high reductioncold-rolling and further heattreating. Such a cold-rolled strip has themost favorable magnetic orientation of the grain along the length of thestrip and my method of producing magnetic cores from strip materialmakes it possible to make use of this favorable magnetic orientation.

If desired, a plurality of cores may be wound on to a current conductingwinding structure either on different legs of the winding structure, oron different portions of the same leg, or if desired, a plurality ofconcentric cores may be provided, one of which is formed about theother. In Fig. 15 a single winding II is shown with a single core l2 butpreferably a second core is wound about the other leg 41 of the windingH in order that the core material will substantially fill the window 48formed in the winding structure and provide maximum efiiciency for thecopper employed in the current conducting winding. The relationship oftwo strip wound cores is shown in Fig. 16. In Fig. 16, the windingstructure H consists of a plurality of windings 49, 50 and 5|, thewidths of which may be made different so that the core winding forms maybe substantially filled and the maximum utilization is obtained of bothcurrent conducting winding material and magnetic material. If only onewound core I2 is to be employed, the winding structure may be shaped asillustrated in Fig. 17 in order to have the window 48 substantiallyfilledby magnetic core material.

In accordance with the provisions of the patent statutes, I havedescribed the principle of operation of my invention together with theapparatus which I now consider to represent the best embodiment thereofbut I desire to have it understood that the apparatus shown is onlyillustrative and that the invention may be carried out by other means.

'What I claim as new and desire to secure by Letters Patent of theUnited States is:

Stationary induction apparatus comprising a current conducting windingstructure, an insulating tube surrounding one leg of the windingstructure, said tube having a groove cut therein axially, a coil ofmagnetic strip material wound into a core surrounding said insulatingtube, the inner end of said strip having a crimp fitting into the groovein said tube.

FREDERICK F. BRAND.

